Unit 1 Earth

Question 1

Earth’s shape

Answer 1

Oblate spheroid

Question 2

Equator

Answer 2

The line around the Earth’s widest point as aligned with its rotation, 0 degrees latitude. Divides the northern and southern hemispheres.

Question 3

Tropics

Answer 3

Two lines around the Earth making marking the furthest north (Cancer, 21st June) and south (Capricorn, 21st December) that the Sun appears at the zenith. 23.5 degrees north and south.

Question 4

Latitude

Answer 4

Angle of measurement taken from the line of the Equator (0 degrees) down to the South Pole (-90 degrees) and up to the North Pole (+90 degrees). Gives an angle North-South.

Question 5

Longitude

Answer 5

An angle of measurement taken from a North-South line running through Greenwich, London, UK. Gives an angle East-West.

Question 6

Pole

Answer 6

Geographic: the places on the Earth’s surface that mark the Earth’s axis of rotation. Magnetic: the places on the Earth’s surface that mark the emergence of it’s magnetic field lines.

Question 7

Horizon

Answer 7

The furthest visible part of the Earth from an observer’s location (at a perfectly flat place); nothing beyond it can be seen due to the curvature of the Earth.

Question 8

Meridian

Answer 8

Wherever an observer is, the line that runs from the South to the North across the sky.

Question 9

Zenith

Answer 9

Wherever an observer is , this is directly up, 90 degrees from the horizon in all directions.

Question 10

Van Allen Belts

Answer 10

Layers of charged particles surrounding the Earth which are held in place by the magnetic field. These layers of radiation stop high speed electrons harming life on Earth.

Question 11

Earth’s diameter

Answer 11

13000km

Question 12

Solar day

Answer 12

24hrs

Question 13

Earth rotational period

Answer 13

23hrs 56mins

Question 14

Evidence that the Earth is not flat.

Answer 14

Ships disappear over the horizon.
Satellites orbit the Earth.
Curvature of the Earth’s shadow during a partial lunar eclipse.

Question 15

Tilt of the polar axis.

Answer 15

66.5 degrees to the plane on which it orbits (the ecliptic).

The Sun resides over latitudes between 23.5 degrees between the equinoxes.

Question 16

Prime Meridian.

Answer 16

North-south line running through Greenwich, London where longitude is measured from (0 degrees east/west).

Question 17

Skyglow.

Answer 17

A form of light pollution that hinders our view of the night sky.

Question 18

Sources of light pollution.

Answer 18

Floodlights.
Street/motorway lights.
Domestic/industrial security lamps.
Lights in car parks/shopping centres etc.

Question 19

How did Eratosthenes measure the Earth’s circumference?

Answer 19

Eratosthenes was in Alexandria and found that on the 21st June the Sun was not directly overhead. The following year he was in Syene and measured the length of the shadow of a stick. The year later he did the same in Alexandria. Using triganometry and he calculated that Alexandria was 7 degrees further around the Earth than Syene. Eratosthenes estimate the distance from Alexandria to Syene and calculated the circumference by find the distance of 1degree and multiplying it by 360 degrees.

Question 20

What gases are in the Earth’s atmosphere?

Answer 20

Nitrogen (78%), oxygen (21%), argon (1%), carbon dioxide (0.04%), water vapour (1%) and traces of other gases.

Question 21

What is 100km above the Earth’s surface?

Answer 21

The Kármán Line (where astronauts generally agree the edge of the atmosphere is).

Question 22

Benefits of having an atmosphere.

Answer 22

Absorption of harmful UV Ray’s which can cause skin cancer.
Absorption of harmful X-Ray’s and gamma rays.
Regulates the temperature allowing water to exist.
Provides oxygen to breathe.
Partly protects us from meteorites.

Question 23

What are some of the drawbacks, for astronomers, of the atmosphere?

Answer 23

Refraction of light as it passes through the turbulent air causing stars to twinkle, restricting resolution.
Selective scattering of shorter wavelengths preventing observations during the day.
Absorption and reflection of certain electromagnetic waves from space meaning most Gamma Ray, X-Ray and uv Ray telescope must be in orbit.

Question 24

What do electrons in the ionosphere do to the longest radio waves?

Answer 24

Reflect them.

Question 25

How are some of the shorter microwaves absorbed?

Answer 25

They are absorbed by water vapour (H2O) and oxygen (O2).

Question 26

What gases is most IR radiation absorbed by?

Answer 26

H2O, CO2 and Methane (CH4).

Question 27

What gases are most UV wavelengths absorbed by?

Answer 27

O3 and O2.

Question 28

X-rays and gamma rays are absorbed by which gases?

Answer 28

Oxygen and Nitrogen.

Question 29

Two types of telescope.

Answer 29

Refractor- convex lens collects the light and brings it to a focus.
Reflector-curved mirror collects light.

Question 30

What is a lens or mirror called?

Answer 30

An objective. It’s size refers to it’s diameter.

Question 31

Advantages of large telescopes.

Answer 31

They collect more light in proportion to area and have a higher resolution in proportion to diameter.

Question 32

How many times higher resolution does a 10 metre telescope have over a 2 metre telescope.

Answer 32

Collects 25 times more light so,

25=5^2 so has 5 times as much resolution.

Question 33

More light entering a telescope means…

Answer 33

smaller objects become visible.

Question 34

Most modern telescopes are reflectors. Why?

Answer 34

Mirrors can be manufactured with greater precision and are easier to transport.

Question 35

Ideal observation sites consider…

Answer 35

atmospheric conditions such as cloud cover, air turbulence, sky brightness, water vapour content, access, utilities likelihood of earthquakes and ground stability.

Question 36

Advantages of using telescopes in orbit.

Answer 36

No atmosphere to blur/reduce resolution of the images.
No light pollution.
No adverse weather problems.
Longer observation periods.
Ability to detect “other” wavelengths such as gamma rays, IR and X-rays.

Question 37

Disadvantages of using telescopes in orbit.

Answer 37

Reduced lifetime.
Difficult/impossible to repair or upgrade.
More expensive to build and launch into orbit.

Question 38

What are the Van Allen Belts?

Answer 38

Two doughnut shaped rings, made of high energy particles, that spin above the Earth. The lower belt can be hazardous when astronauts or experiments if exposed to the radiation for a long time. The Inner Belt is made of mainly protons, whereas the outer is made mainly of electrons.